Crushers are commonly used in the mining and minerals processing industry in order to break down large solid materials into smaller pieces for further processing or transport. Some examples of crushers include jaw crushers, cone crushers, cylindrical roll crushers, and gyratory crushers. Large pieces of material are typically broken down in a crusher through a moving component which drives the material against a stationary component with sufficient force to fracture and fragment the material to smaller, more manageable pieces. One type of crusher is a gyratory crusher which comprises a moving mantle and a stationary concave. Each of the mantle and concave are covered by liners. The mantle moves on an eccentric in a circular orbit within the concave, causing an annular gap at each radial location inside the crusher to narrow and widen as the mantle moves around its orbit. The narrowest gap between the mantle liner and the concave liner is known as the closed-side setting (CSS). The widest gap between the mantle liner and the concave liner is known as the open-side setting (OSS).
Operators of gyratory crushers try to maintain the CSS at a constant value to ensure efficient and predictable operation. Due to the frictional wear and tear on the concave liner and the mantle liner from the crushing operation, the CSS will get larger over time, and adjustments must be periodically made to ensure a constant CSS is maintained. It is critical to know the crusher gap width as it relates to the CSS to ensure the crushed product size is optimum for the mill feed.
Adjustments may be made by varying the position of the mantle (usually in the vertical direction) relative to each other, or the concave liner and/or the mantle liner may be replaced when excessively worn and adjustment is no longer feasible. Disadvantageously, known methods for measuring the CSS requires the operator to lower a lead ball attached to rope into the crusher chamber/pocket. Usually it is placed on the ore inside the crusher pocket. As the ore goes through the crusher the lead ball gets “squished” and the operator raises the lead ball back up so they can manually measure the width of the lead ball. This is the measurement they use to determine the mantle position, allowing for determination of the wear on the mantle from the previous adjustment. Also, the manual measurement presents certain safety concerns, as a person must be brought into the vicinity of the crusher while becoming exposed to crushed rock, dust, and debris. In another method, mantle wear is measured with 3-dimensional laser imaging. This requires shutting down the crusher and the use of an overhead crane for the imaging.
One system for measuring CSS is disclosed in US Publication No. 20130231892. It is for measuring the displacement of a surface in a material handling system relative to a base reference. The system includes scanning means to generate point cloud data of the surface relative to a reference point to define a three-dimensional image of the surface, storage means to store base reference data in respect of the base reference, and processing means to process the point cloud data and the base reference data to determine the relative displacement of the surface with respect to the base reference. The processing means includes a referencing means to orientate the point cloud data relative to key reference data of the base surface and transforming the point cloud data and the base reference data into a common co-ordinate system, and displacement processing means to calculate the displacement between the surface and the base reference using both sets of data in the co-ordinate system. In this way, it maps the surface of the parts of interest. This system has been determined to be very expensive and overly complex. Further, the crusher or mill must be stopped and decontaminated before scanning can be done. The scanner is then positioned in the mill or crusher using an overhead crane, the scans are done to provide data and then the scanner is removed. The data are then analyzed to provide a three-dimensional map. The scanner then needs to be removed before operations can start again. Accordingly, this is a disruptive process that results in significant down time.
What is needed is a safe, quick method for determining CSS or OSS. Preferably, this could be done without shutting the crusher down. Preferably, calibration would be done quickly and safely, without the need for a worker to unsafely drop a lead ball into the crusher chamber and pull it out again. A system to allow such a method is therefore also needed. It would be preferably if the laser emitter and camera could be mounted in a location that is not subject to vibration.